Such paper is rough; could be smoother (5)

I believe the answer is:

emery

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'be smoother' is the definition.
(emery paper is used to smooth things)

I can't explain the rest of the clue.

(Other definitions for emery that I've seen before include "Black abrasive" , "Abrasive material" , "hard stuff" , "Hard, grey-black mineral used as 11 down" , "Coating on paper used as an abrasive" .)

I've seen this clue in The Globe and Mail.

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